Fig. 59.2 Failure to pace. The first six beats show a pacing spike followed by a paced QRS complex (VVI pacemaker), then the pacing spike occurs (arrowed) but no paced beats follow, ‘failure-to-pace’. Fortunately, the underlying heart rhythm, complete heart block, rapidly emerged. The pacemaker output was set too low; the problem resolved when it was increased.
Anti-bradycardia pacemakers comprise the majority of pacemakers (88% of the 35 000 pacemaker device implanted in the UK in 2004). They determine whether normal cardiac electrical activity has occurred; if so, they are silent, if not, then they stimulate the heart to beat. The common indications are: third degree atrioventricular (AV) block (30% of implants), sick sinus syndrome (25%), atrial fibrillation with bradycardia (20%), second degree heart block (15%), others (10%). Except in rare circumstances (see Chapter 60) they do not prevent tachycardias (e.g. in atrial fibrillation [AF] with pauses antitachycardic medication is still needed post-pacemaker implantation).
Pacemaker implantation
Pacemakers are implanted under local anaesthetic, in the left upper chest of right-handed individuals. The skin is cut, the cephalic vein identified and opened, the electrode introduced and pushed into the relevant heart chamber, guided into position under X-ray imaging, tested (see below), stitched so it cannot withdraw from the heart, and connected to the generator. The generator is inserted into a pocket made medially in the chest, over pectoral major and under the dermis/subcutaneous fat. The skin wound is sewn up. The procedure takes 30–60 min. The complication rate is low (pneumothorax, haemothorax, pacemaker infection, arrhythmias).
The paced ECG
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